A single in-line memory module (SIMM) comprises a generally planar substrate on which a complex array of circuitry is disposed. The circuitry on the SIMM may include integrated circuit chips or other such intelligent components that are essential to the operation of computers, office machines, telecommunication equipment or other such electrical or electromechanical devices. One edge of the planar substrate of the SIMM typically is provided with a linear array of discrete conductive regions which are electrically connected to the other circuitry on the SIMM, and which enable the SIMM to be electrically engaged with a socket.
The typical prior art SIMM socket includes a molded plastic housing having an elongated slot for receiving the edge of the SIMM. The socket further includes electrically conductive terminals spaced along the length of the slot to electrically contact the discrete conductive regions of the SIMM.
It is desirable to achieve high normal contact forces between the terminals of the socket and the discrete conductive regions along the edge of the SIMM. However, it also is necessary to minimize the insertion forces as the edge of the SIMM is urged into contact with the terminals of the socket. Many prior art SIMM sockets are constructed for a mere pushing and pulling of the SIMM along its own plane into the slot of the socket. However, push-pull SIMM sockets make it difficult to achieve both a low insertion force and a high normal contact force between the terminals and the edge of the fully inserted SIMM. More recent prior art SIMM sockets are designed to enable the SIMM to be inserted into the slot of the socket in a first angular alignment with a low insertion force, and then enable the SIMM to be rotated into a second angular alignment in which a high normal contact force is exerted by the terminals against the discrete conductive regions of the SIMM. These prior art SIMM sockets further include means for defining the range of rotation of the SIMM corresponding to optimum contact forces between the terminals of the socket and the conductive regions of the SIMM. Additionally, these prior art SIMM sockets include polarization means, positioning projections and latches all for properly aligning, positioning and retaining the SIMM in the socket. Examples of such prior art SIMM sockets that have proved to be extremely successful are shown in U.S. Pat. No. 4,575,172 which issued to Walse et al. on Mar. 11, 1986 and U.S. Pat. No. 4,713,013 which issued to Regnier et al. on Dec. 15, 1987. The two above identified patents are assigned to the assignee of the subject invention, and the disclosures thereof are incorporated herein by reference.
Electronic devices such as computers, office machines and telecommunications equipment continue to become both more complex and smaller. These simultaneous trends necessarily require electrical components having lower profiles and internal circuitry of much greater density. The more closely disposed components and the associated electrical connectors create the potential for interference or cross-talk between adjacent arrays of signal carrying circuits. Additionally, the very close proximity of these electrical components creates the potential for local generation of undesirably high temperatures that may not be adequately dissipated. The close spacing of connectors also can create the potential for inadvertent contact between the SIMM and the fragile solder tails of a socket as the SIMM is being inserted or removed.
The prior art has included socket means for increasing the density of the circuitry in an electrical apparatus. In particular, complex SIMM socket housings have been developed for receiving a plurality of SIMMs therein. For example, a connector for receiving two SIMMs is shown in U.S. Pat. No. 4,756,694 which issued to Billman et al. on July 12, 1988. The connector shown in U.S. Pat. No. 4,756,694 is constructed for the above described pushing and pulling of the SIMM into or out of the socket, such that in their fully seated conditions the SIMMs are parallel to one another and aligned to the plane of the board on which the sockets are mounted at an angle of approximately 30.degree.. As noted above, the push-pull arrangement required by the connector shown in U.S. Pat. No. 4,756,694 is undesirable for many applications. Furthermore, the dual socket arrangements as shown in U.S. Pat. No. 4,756,694 necessarily requires a dedicated socket housing that is not likely to be widely applicable from one electrical apparatus to the next. The tooling costs associated with the housings for such connectors is very high. Thus, the dual socket shown in U.S. Pat. No. 4,756,694 requires a significant initial investment in a socket that may have limited applicability. Also, the acute angle alignment of the SIMM to the circuit board requires a higher profile than is available for many applications, such as the various boards for peripherals that may be plugged into a computer.
Prior art sockets with ground plates or shields also are employed in the prior art. In the typical prior art socket, the ground plate will mechanically attach to an exterior region of a socket assembly to extend around a plurality of exterior surfaces for providing the desired grounding and shielding functions. An example of such a grounded or shielded connector is shown in U.S. Pat. No. 4,623,211 which issued to Dambach et al. on Nov. 18, 1986 and which is assigned to the assignee of the subject invention. Still other such grounded or shielded connectors are shown in U.S. Pat. No. 4,806,109 which issued to Manabe et al. on Feb. 21, 1989 and in U.S. Pat. No. 4,874,319 which issued to Hasircoglu on Oct. 7, 1989. The prior art grounded or shielded connectors described above have achieved various degrees of commercial and engineering acceptance, but are not adapted for use with SIMM sockets.
Accordingly, it is an object of the subject invention to provide a SIMM socket assembly for efficiently receiving a plurality of SIMMs.
It is another object of the subject invention to provide a SIMM socket assembly which comprises a plurality of separate SIMM sockets that are assembled into a tiered high density configuration.
It is another object of the subject invention to provide a SIMM socket assembly having shield means for preventing interference and cross-talk between adjacent circuits.
It is another object of the subject invention to provide a modular assembly of components for forming a high density tiered SIMM socket assembly.